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Electrocardiographic Terms 

Electrocardiographic Terms

Harriet S. Meyer

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Electrocardiographic Terms

International standardization of electrocardiographic nomenclature dates back to the mid-20th century.1-4

The preferred abbreviation for electrocardiogram and electrocardiographic in JAMA and the Archives Journals is ECG, not EKG. In the following examples of ECG terms note the use of capitals, lowercase letters, subscripts, and hyphens.


Leads (recording electrodes) are designated as follows:

Types of Leads


Standard (bipolar) leads


Augmented limb leads/unipolar extremity leads

(a, augmented; V, voltage; R, right arm; L, left arm; F, foot)

aVR, aVL, aVF

Inverted aVR lead


(Unipolar) precordia (chest) leads

V1, V2, V3, V4, V5, V6, V7, V8, V9

Right precordial leads

V1R, V2R, V3R, V4R, V5R, V6R

Modified chest lead using V1


Example: The abnormality appeared in leads V3 through V6 [not V3-V6 or V3-6].


The main deflections of the ECG (see Figure 1) are named in alphabetical sequence (P, Q, R, S, T, U), a usage that dates back to the inventor, Willem Einthoven.2 Other deflections use initial letters of the entity being described.

Figure 1. Electrocardiographic deflections (schematic).

Figure 1. Electrocardiographic deflections (schematic).

As a guide, hyphens usually do not link deflection terms in the same PQRSTU complex (eg, QT) but do link deflections in different waves (eg, R-R), with the exception of ST-T. The following are examples of terms descriptive of deflections and patterns in ECG tracings:

delta wave (preferred over Δ wave)

F wave (atrial flutter wave)

f wave (atrial fibrillation wave)

J point, J junction (junction of QRS complex and ST segment; do not confuse with the J curve in hypertension)

J-ST axis, vector

P wave, axis, etc

PR interval, segment, etc (not P-R)

Q wave, q wave

qR complex

QR-type complex

QRS complex, configuration, axis, duration, etc

qrs complex, etc

QRS-T complex

QS wave, qs wave

QT interval, prolongation, etc (not Q-T)

QTc (corrected QT interval)

R wave, r wave, R′ wave, r′ wave


R-R interval

rS, RS, Rs complex, configuration, etc

R/S (ratio)

rSR′ pattern

S wave, s wave

S′ wave, s′ wave

ST segment, depression, axis, etc (not S-T)

ST-segment abnormality

ST-T segment, elevation, changes, axis, etc (not S-T-T)

T wave, axis, etc

Ta wave (atrial repolarization)

TQ segment

U wave

When terms such as the foregoing are used as modifiers, use a hyphen before the modifying noun (see also 8.3, Punctuation, Hyphens and Dashes).

P-wave duration

Q-wave irregularity

non–Q-wave myocardial infarction

ST-segment depression (not S-T)

The following symbols are used in connection with paced ECGs:


atrial stimulus


ventricular stimulus


interval from atrial stimulus to succeeding ventricular stimulus


interval from atrial stimulus to conducted spontaneous ventricular depolarization


interval from spontaneous atrial depolarization to succeeding “atrial-synchronous” ventricular stimulus

Capital letters are used to describe generic ECG deflections.

Improper paper speed will spuriously alter the QRS configuration. [not qrs configuration]

In reference to an individual ECG tracing, or in descriptions of some specific ECG patterns, capitals may indicate larger waves and lowercase letters smaller waves; in practice, this most often applies to the Q, R, and S waves.

Pathologic Q waves occur in myocardial infarction.

The q wave in aVF and the Rr′ pattern in lead V3 in this patient’s ECG were considered normal findings.

An rSR′ complex in the anterior chest leads and qRs in the left chest leads may indicate right bundle-branch block.

Lead and tracing terms may be combined to describe pattern and location together.




R wave in lead I


R wave in aVL


S wave in lead III


R wave in V3

S1Q3T3 pattern

Prominence of S wave in lead I, Q wave in lead III, and T-wave inversion in lead III

SV1 + RV5

Sum of voltages of S wave in V1 and R wave in V5

The P axis, QRS axis, ST axis, and T axis are specified with a plus or minus sign followed by the number of degrees in arabic numerals, eg, +60°, −30°.

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